1. Field of the Invention
The present invention relates to a gas turbine, and to a bleeding method thereof, that is rotationally driven using combusted gas from a combustor.
2. Description of Related Art
In a gas turbine plant, compressed air from a compressor is guided into a combustor, and the high-temperature gas generated during combustion of the compressed air together with a fuel is guided into the gas turbine to drive the gas turbine. A typical design is one in which a portion of the compressed air is introduced into a cooling device as bleed air and is cooled. The cooled bleed air is subsequently guided to stationary and moving blades on the gas turbine side, and is used to cool these blades and as sealing air between the moving and stationary blades.
An example of a structure for bleeding in a conventional gas turbine will be explained below with reference to FIG. 3. A compressor, which would be to the left on the page but is not shown in the figure, is coaxially connected to the gas turbine. Note that in the following discussion, the left side of the drawing will be referred to as the “upstream side” and right side of the paper will be referred to as the “downstream side”. Furthermore, the direction of the rotation axis (to the left and right on the paper) of a rotor of the gas turbine will be referred to as the “axial direction”.
In FIG. 3, plural moving blades 1b, 2b, 3b, and 4b are coaxially disposed annularly around a first stage rotor disk 1a, a second stage rotor disk 2a, a third stage rotor disk 3a, and a fourth stage rotor disk 4a, respectively. Plural stationary blades (not shown) are annularly disposed so that each stationary blade is coaxial to each stage moving blade on the interior side of a vehicle, which is not shown, at the downstream side of moving blades 1b to 4b. These stationary blades are corresponding to moving blades 1b to 4b at the downstream side respectively to compose the first stage unit 1 to the fourth stage unit 4.
Furthermore, seal disk 5 is coaxially connected to first stage unit 1 at the upstream. Disk hole 5a is penetrating holes through which bleed air f from the upstream passes toward moving blades 1b to 4b of stage units 1 to 4. In seal disk 5, plural disk holes 5a are formed centered about the axis and at equal angle intervals from one another.
Plural radial holes 1a1 are formed in rotor disk 1a of first stage unit 1 with equal angle intervals from one another. Radial holes 1a1 lead a portion of bleed air f after passing through disk holes 5a into a cooling flow path formed in moving blade 1b. Furthermore, in rotor disk 1a, plural disk holes 1a2 are formed for supplying the rest of bleed air f into second stage unit 2 with equal angle intervals from one another.
As similar to first stage unit 1, plural radial holes 2a1 and 3a1, and 2a2 and 3a2 are formed in rotor disk 2a of second stage unit 2 and rotor disk 3a of third stage unit 3, respectively.
In rotor disk 4a of fourth stage unit 4, plural radial holes 4a1 are formed.
A bleeding method of a conventional gas turbine which has the above-described constitution will be explained.
A portion of bleed air f supplied from the final stage of the compressor (the final compressing stage) is supplied into a space between inside shrouds of the stationary blades and inside shrouds of moving blades 1b of first stage unit 1 in order to seal to prevent from leaking combustion gas. The rest of bleed air f is supplied toward seal disk 5 which is rotating, and supplied rotor disk 1a of first stage unit 1 after passing through disk holes 5a. 
Bleed air f which has passed through radial holes 1a1 is supplied into a flow path formed in each first stage moving blade 1b to cool first stage moving blades 1b from thereinside. On the other hand, bleed air f which has passed through disk holes 1a2 is supplied into rotor disks 2a of second stage unit 2. Furthermore, a portion of bleed air f is used for cooling moving blades 2b in second stage unit 2, similar to first stage unit, and the rest of bleed air f is supplied into third stage unit 3. Similarly, a portion of bleed air f is used for cooling moving blades 3b in third stage unit 3 and the rest of bleed air f is supplied into fourth stage unit 4 which is the final stage for cooling moving blades 4b in fourth stage unit 4.
In the above-described conventional gas turbine, there are some problems as explained below.
Since bleed air f supplied from the compressor has too high pressure to use for cooling moving blades, supply pressure of bleed air f is decreased by passing bleed air f through narrow radial holes 1a1, 2a1, 3a1, and 4a1, and passing bleed air f through plural orifice plates (not shown) which are provided in moving blades 1b to 4b in order to control a flow rate, and as a result, the efficiency becomes deteriorated.
In the conventional gas turbine plant, a portion of power generated in the gas turbine is used for rotational driving force of the above-described compressor. Bleed air f is compressed by the compressor so as to have high pressure. However, for using as bleed air f, the pressure of the compressed air must be decreased. Therefore, the efficiency of the rotational driving power becomes lower, and when generation efficiency in a power plant using the gas turbine plant is considered, an amount of power to be used for rotating a generator by the gas turbine decreases, so that the generation efficiency decreases.